Commentary: Cost effectiveness of antenatal screening for cystic fibrosis

BMJ 1995; 311 doi: (Published 02 December 1995) Cite this as: BMJ 1995;311:1463
  1. Angus Clarke, senior lecturer in clinical geneticsa
  1. aDepartment of Medical Genetics, University of Wales, College of Medicine, Cardiff CF4 4XW

    As a clinical geneticist commenting on this paper I will consider some assumptions made by the authors and the context in which antenatal screening for cystic fibrosis might be carried out.

    There are four aspects of this study that raise important questions. The first concerns the provision of information before the test and the influence of this on the uptake of testing. From the reports of (non-pregnant) population screening for cystic fibrosis in Britain, the mode of invitation seems to be a major influence on most people's decisions about testing. For example, uptake after invitation by letter has been about 9-12%; after active opportunistic invitation to an appointment for counselling and testing 25%; and after opportunistic invitation to on the spot testing 66-87%.1 2 This can be interpreted as the compliance of and uninterested public in the face of professional enthusiasm for testing. Given this background, how are we to understand the high rates of uptake reported in prenatal screening programmes for carriers of cystic fibrosis, up to 100%?3 4 5 6 7 Is the higher uptake the result of greater motivation of women or couples who now regard the test as relevant to them and who would not have seen the relevance of the test in advance of the pregnancy? Or do women feel coerced into accepting any prenatal screening test if it is presented as a test “to ensure your baby will be healthy”? Or is it passive compliance again? The first explanation seems patronising, whereas the other may be accurate but disturbing. The way in which the test is offered may need to be structured differently to permit a choice that is experienced by women as real.

    The second issue is closely related to the first. It is not costed in this paper, but it is crucial to any population screening programme in which the point of screening is to give information to families who want it rather than to deliver benefits to affected people or improve the (genetic) health of the public. The staff offering any such test require education both about the facts of the disease and the screening programme. Without continuing education for all relevant health professionals, women and couples will be recruited into the programme without having adequately thought through the issues. This problem has also arisen in the newborn screening programme for Duchenne muscular dystrophy in Wales, still under psychosocial evaluation, where the uptake rate (about 95%) is disconcertingly high and where we are assessing ways of reducing it.

    The next issue concerns couple screening for carriers of cystic fibrosis. This is a difficult test to offer, and I am pleased that Cuckle and colleagues have found it to be relatively unattractive. In addition to its other disadvantages it entails deliberately withholding information from many tested patients, and interested members of the families of identified carriers are unable to benefit from cascade carrier testing.8

    The final point concerns the genetic counselling that is made available to high risk pregnant couples—that is, couples in which both parents are definite carriers of cystic fibrosis, with a 1 in 4 chance of the current pregnancy being affected. It is supposed that this could adequately be provided for 80 identified couples a year by a genetics nurse specialist working one session a week. Of the 80 couples identified by the screening programme, 20 would have an affected fetus and would go on to have either a termination of pregnancy or an affected child. The counselling of all such families and the provision of support to them during and after their decision making is difficult and demanding, and it is easy to underestimate the time required for this and the level of knowledge and skill required by the counsellor. Only some genetics nurses have an appropriate background to fulfil this role—and in any case there are very few such trained nurses or genetics associates available in Britain. This type of work is quite distinct from offering a population screening test, when nurses and midwives will more readily be able to acquire the necessary knowledge and skills and the appropriate attitudes. A more detailed clinical and scientific knowledge of cystic fibrosis is required for such counselling after the test than for the initial offer of testing. Cuckle and colleagues have assumed a minimal input of counselling in their paper, perhaps because they confuse these two roles. This will have led them to underestimate the costs of providing satisfactory genetic counselling.

    Before health authorities consider purchasing antenatal screening for carriers of cystic fibrosis they should consider what benefits they would hope for and how these would be measured.9 10 11 Perhaps such screening would best be made available to the general population without active promotion and without being targeted at the antenatal clinic.12


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